Strengthened expandable baskets for medical probes and medical probes containing strengthen expandable baskets

ABSTRACT

An example expandable basket assembly for a medical probe may include a plurality of spines extending along a longitudinal axis from a proximal central proximal spine portion to a distal spine portion. The distal spine portion may define a cloverleaf structure disposed radially around the longitudinal axis. The cloverleaf structure may define a central cutout with a central area disposed about the longitudinal axis. The cloverleaf structure may include a sinusoidal-like member extending from one spine to an adjacent spine in a direction around the longitudinal axis. The sinusoidal-like member may include a plurality of distal facing portions, a plurality of proximal facing portions, and at least one side connector connecting two adjacent distal facing portions to one another. The at least one side connector may strengthen a distal end of the expandable basket.

CROSS REFERENCE TO RELATED APPLICATION

This application is claims priority under 35 U.S.C. § 119 to U.S. Provisional Patent Application No. 63/336,023 filed Apr. 28, 2022, the entire contents of which is fully incorporated herein by reference.

FIELD

The present invention relates generally to medical devices, and in particular catheters with electrodes, and further relates to, but not exclusively, catheters suitable for use to induce irreversible electroporation (IRE) of cardiac tissues.

BACKGROUND

Cardiac arrhythmias, such as atrial fibrillation (AF), occur when regions of cardiac tissue abnormally conduct electric signals to adjacent tissue. This disrupts the normal cardiac cycle and causes asynchronous rhythm. Certain procedures exist for treating arrhythmia, including surgically disrupting the origin of the signals causing the arrhythmia and disrupting the conducting pathway for such signals. By selectively ablating cardiac tissue by application of energy via a catheter, it is sometimes possible to cease or modify the propagation of unwanted electrical signals from one portion of the heart to another.

Many current ablation approaches in the art tend to utilize radiofrequency (RF) electrical energy to heat tissue. RF ablation can have certain rare drawbacks due to operator's skill, such as heightened risk of thermal cell injury which can lead to tissue charring, burning, steam pop, phrenic nerve palsy, pulmonary vein stenosis, and esophageal fistula. Cryoablation is an alternative approach to RF ablation that can reduce some thermal risks associated with RF ablation but may present tissue damage due to the very low temperature nature of such devices. Maneuvering cryoablation devices and selectively applying cryoablation, however, is generally more challenging compared to RF ablation; therefore, cryoablation is not viable in certain anatomical geometries which may be reached by electrical ablation devices.

Some ablation approaches use irreversible electroporation (IRE) to ablate cardiac tissue using nonthermal ablation methods. IRE delivers short pulses of high voltage to tissues and generates an unrecoverable permeabilization of cell membranes. Delivery of IRE energy to tissues using multi-electrode catheters was previously proposed in the patent literature. Examples of systems and devices configured for IRE ablation are disclosed in U.S. Patent Pub. No. 2021/0169550A1, 2021/0169567A1, 2021/0169568A1, 2021/0161592A1, 2021/0196372A1, 2021/0177503A1, and 2021/0186604A1, each of which are incorporated herein by reference.

Regions of cardiac tissue can be mapped by a catheter to identify the abnormal electrical signals. The same or different catheter can be used to perform ablation. Some example catheters include a number of spines with electrodes positioned thereon. The electrodes are generally attached to the spines and secured in place by soldering, welding, or using an adhesive. Furthermore, multiple linear spines are generally assembled together by attaching both ends of the linear spines to a tubular shaft (e.g., a pusher tube) to form a spherical basket. Due to the small size of the spines and the electrodes, however, adhering the electrodes to the spines and then forming a spherical basket from the multiple linear spines can be a difficult task, increasing the manufacturing time and cost and the chances that the electrode fails due to an improper bond or misalignment. What is needed, therefore, are devices and methods of forming an improved basket assembly that can help to reduce the time required for manufacturing the basket assembly, alternative catheter geometries, and alternative electrode shapes and sizes in general.

SUMMARY

A medical probe is presented including an expandable basket assembly coupled to a distal end of a tubular shaft. The basket assembly includes a cloverleaf cutout structure at its distal end and spines extending proximally from the cloverleaf structure and coupling to the tubular shaft. The cloverleaf structure includes a sinusoidal-like member extending from one spine to an adjacent spine in a direction around the longitudinal axis. Dimensions of the sinusoidal-like member can be configured to provide a lateral stiffness of the expandable basket assembly within a predetermined range and a maximum peak stress during retraction of the expandable basket assembly into an intermediate catheter such that the maximum peak stress is less than a predetermined threshold. The cloverleaf structure may include one or more side connectors to connect two or more distal facing portions of the cloverleaf structure to one another to increase the strength of the distal end of the spine and prevent breakage.

An example expandable basket assembly for a medical probe may include a plurality of spines extending along a longitudinal axis from a proximal central proximal spine portion to a distal spine portion. The distal spine portion may define a cloverleaf structure disposed radially around the longitudinal axis. The cloverleaf structure may define a central cutout with a central area disposed about the longitudinal axis. The cloverleaf structure may include a sinusoidal-like member extending from one spine to an adjacent spine in a direction around the longitudinal axis. The sinusoidal-like member may include a plurality of distal facing portions, a plurality of proximal facing portions, and at least one side connector connecting two adjacent distal facing portions to one another.

The sinusoidal-like member may extend around (a) a first virtual circle having a first open area of approximately 20% that of the central area, the first virtual circle having its center located at a first distance to the longitudinal axis, (b) a second virtual circle having a second open area of approximately 90% of the first open area, the second virtual circle having its center located at a second distance smaller than the first distance to the longitudinal axis, (c) a third virtual circle having a third open area approximately equal to the first open area, the third virtual circle having its center located at a third distance approximately equal to the first distance to the longitudinal axis, and (d) a fourth virtual circle encircling the sinusoidal-like member comprises an area approximately 14 times greater than the central area and each of the first and third virtual circle is located at a first distance from the central axis while the second virtual circle is located at a second distance of approximately half that of the first distance. The at least one side connector may separate the first and third open areas from the central area.

The at least one side connector may include two or more side connectors.

Portions of the sinusoidal-like member may be tangential to a virtual sphere with its center disposed substantially on the longitudinal axis so that distal edges of the cutout extend a general direction towards the proximal portion.

The expandable basket assembly may include a coating covering the sinusoidal-like member and a central cutout circumscribed by the sinusoidal-like member.

Each of the spines may include at least one retention member extending generally transverse to the spine.

The at least one retention member may include a bow shaped member.

The at least one retention member may include two bow shaped members disposed in opposite direction and transverse to a longer length of each spine.

The at least one retention member may include first and second sets of retention members spaced apart along the spines. The first set may include two bow shaped members disposed in opposite direction and transverse to a longer length of each spine. The second set may include two bow shaped members disposed in opposite direction and transverse to a longer length of each spine so that each electrode is captured between the first and second sets of retention members.

The at least one side connector may have a width ranging from approximately 0.1 mm to approximately 0.4 mm and a length ranging from approximately 0.1 mm to approximately 0.4 mm.

The plurality of spines may be configured to form an approximately oblate-spheroid basket assembly when in the expanded form.

An example medical probe may include a tubular shaft including a proximal end and a distal end. The tubular shaft may extend along a longitudinal axis of the medical probe. The medical probe may further include an expandable basket assembly coupled to the distal end of the tubular shaft. The basket assembly may include a plurality of spines extending along a longitudinal axis from a proximal central proximal spine portion to a distal spine portion. The distal spine portion may define a cloverleaf structure disposed radially around the longitudinal axis. The cloverleaf structure may define a central cutout with a central area disposed about the longitudinal axis. The cloverleaf structure may include a sinusoidal-like member extending from one spine to an adjacent spine in a direction around the longitudinal axis. The sinusoidal-like member may include a plurality of distal facing portions, a plurality of proximal facing portions, and at least one side connector connecting two adjacent distal facing portions to one another.

The sinusoidal-like member may extends around (a) a first virtual circle having a first open area of approximately 20% that of the central area, the first virtual circle having its center located at a first distance to the longitudinal axis, (b) a second virtual circle having a second open area of approximately 90% of the first open area, the second virtual circle having its center located at a second distance smaller than the first distance to the longitudinal axis, (c) a third virtual circle having a third open area approximately equal to the first open area, the third virtual circle having its center located at a third distance approximately equal to the first distance to the longitudinal axis, and (d) a fourth virtual circle encircling the sinusoidal-like member comprises an area approximately 14 times greater than the central area and each of the first and third virtual circle is located at a first distance from the central axis while the second virtual circle is located at a second distance of approximately half that of the first distance. The at least one side connector may separate the first and third open areas from the central area.

The medical probe may include a plurality of electrodes, each electrode of the plurality of electrodes comprises a body defining a hollow portion extending through the body of the electrode so that a spine can be inserted into the hollow portion and retained by the at least one retention member. The at least one side connector comprises two or more side connectors.

The medical probe may include a plurality of electrically insulative jackets each disposed between a respective spine of the plurality of spines and a respective electrode, thereby electrically isolating the respective electrode from the respective spine.

The at least side connector may have a width ranging from approximately 0.1 mm to approximately 0.4 mm and a length ranging from approximately 0.1 mm to approximately 0.4 mm.

The medical probe may include a wire disposed inside a respective jacket the plurality of electrically insulative jackets, the wire is electrically connected to the respective electrode.

The plurality of spines may be configured to form an approximately spherically-shaped basket assembly when in the expanded form.

The central cutout approximates a central circle with the central area. The cloverleaf structure may be disposed within a fourth circle with its center on the longitudinal axis so that portions of the cloverleaf close to the center circle is spaced apart along the longitudinal axis with respect to portions of the cloverleaf close to the fourth circle thereby defining a concave cloverleaf structure.

The cloverleaf structure may be concave with its center extending towards the proximal central spine portion of the basket to approximate a concave surface disposed about the longitudinal axis.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic pictorial illustration of a medical system including a medical probe whose distal end includes a basket assembly with electrodes, in accordance with an embodiment of the present invention;

FIG. 2A is a perspective view of a medical probe in an expanded form, in accordance with an embodiment of the present invention;

FIG. 2B is a sectional view of a cross-sectional plane orthogonal to the longitudinal axis to show the internal components of electrode and spine assembly;

FIG. 2C is a perspective view of electrodes mounted on the insulative jacket with wires running along a spine for connection to each electrode;

FIG. 3A illustrates the medical probe of FIG. 2A with only the underlying spine structure and one electrode disposed on one spine;

FIG. 3B illustrates the spine structure as formed from a tube stock;

FIG. 4A illustrates an end and flattened view of the distal end of the basket spine structure of FIG. 3A as if the entire basket spines are captured flat between two flat plates of glass for viewing by an observer located on the longitudinal axis;

FIG. 4B illustrates the end view of the spine structure of FIG. 4A with design nomenclatures of a cloverleaf structure disposed proximate the distal end of the spine structure of FIG. 3A;

FIG. 5A illustrates a side view of the basket spine structure of FIG. 3A to illustrate a concavity of the cloverleaf structure that can be approximated by a virtual sphere;

FIG. 5B is a close-up of the inset shown in FIG. 5A to show the concavity of the distal central portion of the basket assembly;

FIG. 6A and FIG. 6B illustrate a close-up view showing an electrode;

FIG. 7A illustrates a perspective view of a distal end of a medical probe in an expanded form and including a coated distal end, in accordance with an embodiment of the present invention;

FIG. 7B illustrates the spine structure as formed from a tube stock and including a coated distal end; and

FIG. 7C illustrates a perspective view of a distal end of a medical probe in an expanded form and including a coated distal end with a central opening, in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION

The following detailed description should be read with reference to the drawings, in which like elements in different drawings are identically numbered. The drawings, which are not necessarily to scale, depict selected embodiments and are not intended to limit the scope of the invention. The detailed description illustrates by way of example, not by way of limitation, the principles of the invention. This description will clearly enable one skilled in the art to make and use the invention, and describes several embodiments, adaptations, variations, alternatives and uses of the invention, including what is presently believed to be the best mode of carrying out the invention.

As used herein, the terms “about” or “approximately” for any numerical values or ranges indicate a suitable dimensional tolerance that allows the part or collection of components to function for its intended purpose as described herein. More specifically, “about” or “approximately” may refer to the range of values ±20% of the recited value, e.g., “about 90%” may refer to the range of values from 72% to 108%.

As used herein, the terms “patient,” “host,” “user,” and “subject” refer to any human or animal subject and are not intended to limit the systems or methods to human use, although use of the subject invention in a human patient represents a preferred embodiment. In addition, vasculature of a “patient,” “host,” “user,” and “subject” can be vasculature of a human or any animal. It should be appreciated that an animal can be a variety of any applicable type, including, but not limited thereto, mammal, veterinarian animal, livestock animal or pet type animal, etc. As an example, the animal can be a laboratory animal specifically selected to have certain characteristics similar to a human (e.g., rat, dog, pig, monkey, or the like). It should be appreciated that the subject can be any applicable human patient, for example. As well, the term “proximal” indicates a location closer to the operator or physician whereas “distal” indicates a location further away to the operator or physician.

As discussed herein, “operator” can include a doctor, surgeon, technician, scientist, or any other individual or delivery instrumentation associated with delivery of a multi-electrode catheter for the treatment of drug refractory atrial fibrillation to a subject.

As discussed herein, the term “ablate” or “ablation”, as it relates to the devices and corresponding systems of this disclosure, refers to components and structural features configured to reduce or prevent the generation of erratic cardiac signals in the cells by utilizing non-thermal energy, such as irreversible electroporation (IRE), referred throughout this disclosure interchangeably as pulsed electric field (PEF) and pulsed field ablation (PFA). Ablating or ablation as it relates to the devices and corresponding systems of this disclosure is used throughout this disclosure in reference to non-thermal ablation of cardiac tissue for certain conditions including, but not limited to, arrhythmias, atrial flutter ablation, pulmonary vein isolation, supraventricular tachycardia ablation, and ventricular tachycardia ablation. The term “ablate” or “ablation” also includes known methods, devices, and systems to achieve various forms of bodily tissue ablation as understood by a person skilled in the relevant art.

As discussed herein, the terms “bipolar” and “unipolar” when used to refer to ablation schemes describe ablation schemes which differ with respect to electrical current path and electric field distribution. “Bipolar” refers to ablation scheme utilizing a current path between two electrodes that are both positioned at a treatment site; current density and electric flux density is typically approximately equal at each of the two electrodes. “Unipolar” refers to ablation scheme utilizing a current path between two electrodes, wherein a first electrode experiences a high current density and high electric flux density and is positioned at a treatment site, and a second electrode experiences comparatively lower current density and lower electric flux density and is positioned remotely from the treatment site.

As discussed herein, the terms “biphasic pulse” and “monophasic pulse” refer to respective electrical signals. “Biphasic pulse” refers to an electrical signal including a positive-voltage phase pulse (referred to herein as “positive phase”) and a negative-voltage phase pulse (referred to herein as “negative phase”). “Monophasic pulse” refers to an electrical signal including only a positive or only a negative phase. Preferably, a system providing the biphasic pulse is configured to prevent application of a direct current voltage (DC) to a patient. For instance, the average voltage of the biphasic pulse can be zero volts with respect to ground or other common reference voltage. Additionally, or alternatively, the system can include a capacitor or other protective component. Where voltage amplitude of the biphasic and/or monophasic pulse is described herein, it is understood that the expressed voltage amplitude is an absolute value of the approximate peak amplitude of each of the positive-voltage phase and/or the negative-voltage phase. Each phase of the biphasic and monophasic pulse preferably has a square shape including an essentially constant voltage amplitude during a majority of the phase duration. Phases of the biphasic pulse are separated in time by an interphase delay. The interphase delay duration is preferably less than or approximately equal to the duration of a phase of the biphasic pulse. The interphase delay duration is more preferably about 25% of the duration of the phase of the biphasic pulse.

As discussed herein, the terms “tubular” and “tube” are to be construed broadly and are not limited to a structure that is a right cylinder or strictly circumferential in cross-section or of a uniform cross-section throughout its length. For example, the tubular structures are generally illustrated as a substantially right cylindrical structure. However, the tubular structures may have a tapered or curved outer surface without departing from the scope of the present disclosure.

The term “temperature rating”, as used herein, is defined as the maximum continuous temperature that a component can withstand during its lifetime without causing thermal damage, such as melting or thermal degradation (e.g., charring and crumbling) of the component.

The present disclosure is related to systems, methods or uses and devices which utilize end effectors including electrodes affixed to spines. Example systems, methods, and devices of the present disclosure may be particularly suited for IRE ablation of cardiac tissue to treat cardiac arrhythmias. Ablative energies are typically provided to cardiac tissue by a tip portion of a catheter which can deliver ablative energy alongside the tissue to be ablated. Some example catheters include three-dimensional structures at the tip portion and are configured to administer ablative energy from various electrodes positioned on the three-dimensional structures. Ablative procedures incorporating such example catheters can be visualized using fluoroscopy.

Ablation of cardiac tissue using application of a thermal technique, such as radio frequency (RF) energy and cryoablation, to correct a malfunctioning heart is a well-known procedure. Typically, to successfully ablate using a thermal technique, cardiac electropotentials need to be measured at various locations of the myocardium. In addition, temperature measurements during ablation provide data enabling the efficacy of the ablation. Typically, for an ablation procedure using a thermal technique, the electropotentials and the temperatures are measured before, during, and after the actual ablation.

RF approaches can have risks that can lead to tissue charring, burning, steam pop, phrenic nerve palsy, pulmonary vein stenosis, and esophageal fistula. Cryoablation is an alternative approach to RF ablation that can reduce some thermal risks associated with RF ablation. However maneuvering cryoablation devices and selectively applying cryoablation is generally more challenging compared to RF ablation; therefore, cryoablation is not viable in certain anatomical geometries which may be reached by electrical ablation devices.

IRE as discussed in this disclosure is a non-thermal cell death technology that can be used for ablation of atrial arrhythmias. To ablate using IRE/PEF, biphasic voltage pulses are applied to disrupt cellular structures of the myocardium. The biphasic pulses are non-sinusoidal and can be tuned to target cells based on electrophysiology of the cells. In contrast, to ablate using RF, a sinusoidal voltage waveform is applied to produce heat at the treatment area, indiscriminately heating all cells in the treatment area. IRE therefore has the capability to spare adjacent heat sensitive structures or tissues which would be of benefit in the reduction of possible complications known with ablation or isolation modalities. Additionally, or alternatively, monophasic pulses can be utilized.

Electroporation can be induced by applying a pulsed electric field across biological cells to cause reversable (temporary) or irreversible (permanent) creation of pores in the cell membrane. The cells have a transmembrane electrostatic potential that is increased above a resting potential upon application of the pulsed electric field. While the transmembrane electrostatic potential remains below a threshold potential, the electroporation is reversable, meaning the pores can close when the applied pulse electric field is removed, and the cells can self-repair and survive. If the transmembrane electrostatic potential increases beyond the threshold potential, the electroporation is irreversible, and the cells become permanently permeable. As a result, the cells die due to a loss of homeostasis and typically die by programmed cell death or apoptosis, which is believed to leave less scar tissue as compared to other ablation modalities. Generally, cells of differing types have differing threshold potential. For instance, heart cells have a threshold potential of approximately 500 V/cm, whereas for bone it is 3000 V/cm. These differences in threshold potential allow IRE to selectively target tissue based on threshold potential.

The solution of this disclosure includes systems and methods for applying electrical signals from catheter electrodes positioned in the vicinity of myocardial tissue, preferably by applying a pulsed electric field effective to induce electroporation in the myocardial tissue. The systems and methods can be effective to ablate targeted tissue by inducing irreversible electroporation. In some examples, the systems and methods can be effective to induce reversible electroporation as part of a diagnostic procedure. Reversible electroporation occurs when the voltage applied with the electrodes is below the electric field threshold of the target tissue allowing cells to repair. Reversible electroporation does not kill the cells but allows a physician to see the effect of reversible electroporation on electrical activation signals in the vicinity of the target location. Example systems and methods for reversible electroporation is disclosed in U.S. Patent Publication 2021/0162210, the entirety of which is incorporated herein by reference.

The pulsed electric field, and its effectiveness to induce reversible and/or irreversible electroporation, can be affected by physical parameters of the system and biphasic pulse parameters of the electrical signal. Physical parameters can include electrode contact area, electrode spacing, electrode geometry, etc. examples presented herein generally include physical parameters adapted to effectively induce reversible and/or irreversible electroporation. Biphasic pulse parameters of the electrical signal can include voltage amplitude, pulse duration, pulse interphase delay, inter-pulse delay, total application time, delivered energy, etc. In some examples, parameters of the electrical signal can be adjusted to induce both reversible and irreversible electroporation given the same physical parameters. Examples of various systems and methods of ablation including IRE are presented in U.S. Patent Publications 2021/0169550A1, 2021/0169567A1, 2021/0169568A1, 2021/0161592A1, 2021/0196372A1, 2021/0177503A1, and 2021/0186604A1, the entireties of each of which are incorporated herein by reference.

To deliver pulsed field ablation (PFA) in an IRE (irreversible electroporation) procedure, electrodes should contact the tissue being ablated with a sufficiently large surface area. As described hereinbelow, the medical probe includes a tubular shaft including proximal and distal ends, and a basket assembly at the distal end of the tubular shaft. The basket assembly includes a single unitary structure. The unitary structure can include a plurality of linear spines formed from a planar sheet of material or tube stock and one or more electrodes coupled to each of the spines. The plurality of linear spines can converge at a central spine intersection including one or more cutouts. The cutouts can allow for bending of each spine such that the spines form an approximately spherical or oblate-spheroid basket assembly. It is noted that the cutouts (in various configurations described and illustrated in the specification) allows the basket to be compressed into a much smaller form factor when undeployed (or undergoing a retraction into a delivery sheath) without buckling or plastic deformation.

FIG. 1 is a schematic, pictorial illustration of a medical system 20 including a medical probe 22 and a control console 24, in accordance with an embodiment of the present invention. Medical system 20 may be based, for example, on the CARTO® system, produced by Biosense Webster Inc. of 31 Technology Drive, Suite 200, Irvine, CA 92618 USA. In embodiments described hereinbelow, medical probe 22 can be used for diagnostic or therapeutic treatment, such as for performing ablation procedures in a heart 26 of a patient 28. Alternatively, medical probe 22 may be used, mutatis mutandis, for other therapeutic and/or diagnostic purposes in the heart or in other body organs.

Medical probe 22 includes a flexible insertion tube 30 and a handle 32 coupled to a proximal end of the tubular shaft. During a medical procedure, a medical professional 34 can insert probe 22 through the vascular system of patient 28 so that a distal end 36 of the medical probe enters a body cavity such as a chamber of heart 26. Upon distal end 36 entering the chamber of heart 26, medical professional 34 can deploy a basket assembly 38 approximate a distal end 39 of the medical probe 22. Basket assembly 38 can include a plurality of electrodes 40 affixed to a plurality of spines 214, as described in the description referencing FIGS. 2A, 2B, 2C, 3A, and 3B hereinbelow. To start performing a medical procedure such as irreversible electroporation (IRE) ablation, medical professional 34 can manipulate handle 32 to position distal end 36 so that electrodes 40 engage cardiac tissue at a desired location or locations. Upon positioning the distal end 36 so that electrodes 40 (disposed on an extension structure 38) engages cardiac tissue, the medical professional 34 can activate the medical probe 22 such that electrical pulses are delivered by the electrodes 40 to perform the IRE ablation.

The medical probe 22 can include a guide sheath and a therapeutic catheter, wherein the guide sheath includes the flexible insertion tube 30 and the handle 32 and the therapeutic catheter includes the basket assembly 38, electrodes 40, and a tubular shaft 84 (see FIGS. 2A through 2B). The therapeutic catheter is translated through the guide sheath so that the basket assembly 38 is positioned in the heart 26. The distal end 36 of the medical probe 22 corresponds to a distal end of the guide sheath when the basket assembly 38 is contained within the flexible insertion tube 30, and the distal end 36 (of the tube 30) corresponds to a proximal portion (FIG. 2A) of the basket assembly 38 when the basket assembly 38 is extended from the distal end of the guide sheath. The medical probe 22 can be alternatively configured to include a second handle on the therapeutic catheter and other features as understood by a person skilled in the pertinent art.

In the configuration shown in FIG. 1 , control console 24 is connected, by a cable 42, to body surface electrodes, which typically include adhesive skin patches 44 that are affixed to patient 28. Control console 24 includes a processor 46 that, in conjunction with a tracking module 48, determines location coordinates of distal end 36 inside heart 26. Location coordinates can be determined based on electromagnetic position sensor output signals provided from the distal portion of the catheter when in the presence of a generated magnetic field. Location coordinates can additionally, or alternatively be based on impedances and/or currents measured between adhesive skin patches 44 and electrodes 40 that are affixed to basket assembly 38. In addition to being used for recording ECG signals or acting as location sensors during a medical procedure, electrodes 40 may perform other tasks such as ablating tissue in the heart.

As described hereinabove, in conjunction with tracking module 48, processor 46 may determine location coordinates of distal end 36 of tube 30 inside heart 26 based on impedances and/or currents measured between adhesive skin patches 44 and electrodes 40. Such a determination is typically after a calibration process relating the impedances or currents to known locations of the distal end has been performed. While embodiments presented herein describe electrodes 40 that are preferably configured to deliver IRE ablation energy to tissue in heart 26, configuring electrodes 40 to deliver any other type of ablation energy to tissue in any body cavity is considered to be within the spirit and scope of the present invention. Furthermore, although described in the context of being electrodes 40 that are configured to deliver IRE ablation energy to tissue in the heart 26, one skilled in the art will appreciate that the disclosed technology can be applicable to electrodes used for mapping and/or determining various characteristics of an organ or other part of the patient's 28 body.

Processor 46 may include real-time noise reduction circuitry 50 typically configured as a field programmable gate array (FPGA), followed by an analog-to-digital (A/D) signal conversion integrated circuit 52. The processor can be programmed to perform one or more algorithms and uses circuitry 50 and circuit 52 as well as features of modules to enable the medical professional 34 to perform the IRE ablation procedure.

Control console 24 also includes an input/output (I/O) communications interface 54 that enables control console 24 to transfer signals from, and/or transfer signals to electrodes 40 and adhesive skin patches 44. In the configuration shown in FIG. 1 , control console 24 additionally includes an IRE ablation module 56 and a switching module 58.

IRE ablation module 56 is configured to generate IRE pulses including peak power in the range of tens of kilowatts. In some examples, the electrodes 40 are configured to deliver electrical pulses including a peak voltage of at least 900 volts (V). The medical system 20 performs IRE ablation by delivering IRE pulses to electrodes 40. Preferably, the medical system 20 delivers biphasic pulses between electrodes 40 on the spine. Additionally, or alternatively, the medical system 20 delivers monophasic pulses between at least one of the electrodes 40 and a skin patch.

In order to prevent blood coagulation, system 20 supplies irrigation fluid (e.g., a normal saline solution) to distal end 36 of tube 30 and to the proximal area of basket assembly 38. It is noted that irrigation fluid can be supplied through the flexible insertion tube 30. Control console 24 includes an irrigation module 60 to monitor and control irrigation parameters, such as the pressure and the temperature of the irrigation fluid. It is noted that while the preference for the exemplary embodiments of the medical probe is for IRE or PFA, it is within the scope of the present invention to also use the medical probe separately only for RF ablation (unipolar mode with an external grounding electrode or bipolar mode) or in combination with IRE and RF ablations sequentially (certain electrodes in IRE mode and other electrodes in RF mode) or simultaneously (groups of electrodes in IRE mode and other electrodes in RF mode).

Based on signals received from electrodes 40 and/or adhesive skin patches 44, processor 46 can generate an electroanatomical map 62 that shows the location of distal end 36 in the patient's body. During the procedure, processor 46 can present map 62 to medical professional 34 on a display 64, and store data representing the electroanatomical map in a memory 66. Memory 66 may include any suitable volatile and/or non-volatile memory, such as random-access memory or a hard disk drive.

In some embodiments, medical professional 34 can manipulate map 62 using one or more input devices 68. In alternative embodiments, display 64 may include a touchscreen that can be configured to accept inputs from medical professional 34, in addition to presenting map 62.

FIG. 2A is an illustration of a perspective view of a medical probe 22 including a basket assembly 38 in an expanded form when unconstrained, such as by being advanced out of an insertion tube lumen at a distal end 36 of an insertion tube 30. Probe 22 may include a contact force sensor 400 to determine contact force of the spines against cardiac tissues. Details of the contact force sensor are shown and described in US Patent Application Publication No. US20210077180A1 published Mar. 18, 2021, which disclosure is incorporated by reference herein.

It should be noted that the medical probe 22 illustrated in FIG. 2A lacks the guide sheath illustrated in FIG. 1 . In the expanded form FIG. 2A, spines 214 bow radially outwardly and in the collapsed form (not shown) the spines 214 are arranged generally along a longitudinal axis 86 of insertion tube 30. In FIG. 2A, a plurality of electrically insulative jackets 217 is provided so that each jacket can be disposed between a respective spine 214 of the plurality of spines and a respective electrode 40 of the plurality of electrodes, thereby electrically isolating the plurality of electrodes from the plurality of spines.

As shown in FIG. 2A, basket assembly 38 includes a plurality of flexible spines 214 that are formed at the end of a tubular shaft 84 and are connected at both ends. During a medical procedure, medical professional 34 can deploy basket assembly 38 by extending tubular shaft 84 from insertion tube 30 causing basket assembly 38 to exit insertion tube 30 and transition to the expanded form. Spines 214 may have elliptical e.g., circular, or rectangular that may appear to be flat cross-sections, and include a flexible, resilient material e.g., a shape-memory alloy such as nickel-titanium, also known as Nitinol forming a strut as will be described in greater detail herein. As shown in FIGS. 2A, 2B and 3A, basket assembly 38 has a proximal portion 36 and a distal end 39. The medical probe 22 can include a spine retention hub 90 that extends longitudinally from a distal end of tubular shaft 84 towards distal end 39 of basket assembly 38. As described supra, control console 24 includes irrigation module 60 that delivers irrigation fluid to basket assembly 38 through tubular shaft 84.

Turning to FIG. 3A, the plurality of flexible linear spines 214 converge at a central spine intersection 211 that is also disposed on a longitudinal axis 86 defined by the spines 214. In some examples central spine intersection 211 can include one or more cutouts 212 that allow for bending of the spines 214 when each spine respective attachment end 216 is connected to the spine retention hub 90, described in more detail below.

As shown herein, electrodes 40 positioned on spines 114 of basket assembly 38 can be configured to deliver ablation energy RF and/or IRE to tissue in heart 26. Additionally, or alternatively, the electrodes can also be used to determine the location of basket assembly 38 and/or to measure a physiological property such as local surface electrical potentials at respective locations on tissue in heart 26. The electrodes 40 can be biased such that a greater portion of the one or more electrodes 40 face outwardly from basket assembly 38 such that the one or more electrodes 40 deliver a greater amount of electrical energy outwardly away from the basket assembly 38 i.e., toward the heart 26 tissue than inwardly.

Examples of materials ideally suited for forming electrodes 40 include gold, platinum and palladium and their respective alloys. These materials also have high thermal conductivity which allows the minimal heat generated on the tissue i.e., by the ablation energy delivered to the tissue to be conducted through the electrodes to the back side of the electrodes i.e., the portions of the electrodes on the inner sides of the spines, and then to the blood pool in heart 26.

Referring to FIG. 3A, basket assembly 38 of medical probe 22 is shown without the insulative sleeve 217 or associated wirings to electrodes 40 being disposed inside sleeve 217 to show the novel underlying basket structure 38. Basket 38 includes a single unitary structure that includes a plurality of spines 214 formed from a cylindrical tube stock (FIG. 3B) and treated to cause the spines 214 to bias radially outward. The material for the spine 214 can be nitinol, cobalt chromium, stainless steel, titanium, or combinations hereof.

Referring to FIG. 2A, the spine retention hub 90 can be inserted into the tubular shaft 84 and attached to the tubular shaft 84. Spine retention hub 90 can include a cylindrical member 94 including a plurality of relief lands 96, multiple irrigation openings 98 to allow outflow of irrigation fluid into a volume defined by the basket spines, and hub end 99. Relief lands 96 can be disposed on the outer surface of cylindrical member 94 and configured to allow a portion of each spine 214, such as each spine attachment end 216, to be fitted into a respective relief land 96 of retention hub 90 also known as a coupler for a contact force sensor 400. The attachment end 216 can be a generally linear end of the spine 214. The attachment end 216 can be configured to extend outwardly from the spine retention hub 90 such that the basket assembly 38 is positioned outwardly from the spine retention hub 90 and, consequently, outwardly from the tubular shaft 84. In this way, the spine 214 can be configured to position the basket assembly 38 distally from the distal end of the tubular shaft 84 and distal from the distal end of the insertion tube 30 when the basket assembly 38 is deployed. Reference electrode 95 can be disposed on the projection 94 or on the hub end surface 99. It should be noted that hub 90 in effect can have multiple functions: (1) to retain the spine legs proximally; (2) allow hub 90 (as well as the basket assembly 22) to be connected to distal tube 84; (3) to function as a fluid diverter for irrigation fluid delivered through distal tube 84; and (4) provide a reference electrode 95.

Referring to FIG. 2B, a sectional view of the basket assembly 38 is shown cut-away to show the spines 214 disposed inside jackets 217 with wiring 41 running along the spines 214 and extending through the jacket 217 to connect with the electrode 40 via connection point (e.g., solder pad) 43. FIG. 2C shows a perspective view of an opaque jacket 217 through which wirings 41 can be seen to extend through jacket 217 to respective connection points 43 of electrodes 40. It should be noted that the connection point 43 is not required to be disposed inside the lumen 70 of electrode 40 but can be outside lumen 70 as long as the connection point does not interfere with tissue contact of the electrode 40.

Referring to FIGS. 6A and 6B, in a preferred embodiment, electrode 40 is about 2 mm to about 3 mm long with a width from about 1.5 mm to about 2.5 mm wide and a height of about 0.8 mm to about 1.5 mm. The lumen 70 may have a negative surface area of about 0.4 mm-squared to about 0.7 mm-squared. The lumen 70 is not placed at the geometrical center but is rather offset lower so that the center 86 of lumen 70 is more towards the flat bottom surface 76. This arrangement ensures that more of the top surfaces 78 and 80 of electrode 40 is above the lumen 70 than below lumen 70.

Referring to FIG. 3A, electrode 40 can be located substantially in place with respect to spine 214 by way of a retention member 220 formed integrally with the spine 214. As illustrated in FIG. 3A, i each of the spines 214 can include at least one retention member 220 extending generally transverse to the spine 214. To allow for insertion of the spine 214 through lumen 70 (FIG. 6A) of electrode 40, each spine 214 can be bisected with a central spine member 222 so that empty space 224 is provided to allow retention member 220 to bend inwardly towards the central spine member 222. The shape of retention member 220 can be of any shape as along as such shape serves to allow the member 220 to be compressed for insertion into lumen 70 of electrode 40 and once released to prevent movement of electrode 40 with respect to the retention member 220. In one embodiment, the at least one retention member 220 is shaped in a bow-like configuration with a center of such bow extending away from a periphery of spine 214. In a preferred embodiment, the at least one retention member 222 for each electrode 40 may include two bow shaped members 220 disposed in opposite direction and transverse to a longer length 214L of each spine 214.

In the configuration shown in FIG. 3A, the at least one retention member may have first 220 a, 220 b and second sets 220 c, 220 d of retention members 220 spaced apart along the spines. The first set includes two bow shaped members 220 a, 220 b disposed in opposite direction and transverse to a longer length 214L of each spine 214 and the second set includes two bow shaped members 220 c, 220 d disposed in opposite direction and transverse to a longer length 214L of each spine 214 so that each electrode 40 is captured between the first and second sets of retention members 220 a, 220 b and 220 c and 220 d.

FIG. 3B shows the spine structure 38 a as formed from a tube stock. It is also within the scope of this invention for the spine structure 38 a to be formed form a flat sheet stock, cut and heat treated to achieve the spheroidal basket shape shown herein. The spine structure 38 a illustrated in FIG. 3B can be compressed longitudinally and the spines 214 can expand radially to form the basket shape spine structure illustrated in FIG. 3A of basket assembly 38 illustrated in FIG. 2A.

FIGS. 4A and 4B show the distal portion 39 (FIG. 2A) in which the distal portion 39 of basket assembly 38 of medical probe 22 can be considered as being flattened between two flat sheets of glass. In this viewing configuration, it can be seen in FIG. 4A that distal portion 39 defines a structure 300 resembling a cloverleaf and hence structure 300 will be referred hereafter as a “cloverleaf”. As before, basket 38 in FIG. 4A and FIG. 4B has a plurality of spines 214 extending along the longitudinal axis 86 from a proximal central proximal spine portion 36 to a distal spine portion 39.

In FIG. 4A, the distal spine portion 39 defines a cloverleaf structure FIG. 4A, 300 disposed radially around the longitudinal axis 86. Each clover cutout 212 is aligned along radial axis A, B, C, D, E and F extending orthogonally from axis 86 so that the plurality of spines 214 extend from the proximal central spine portion 36 in an equiangular pattern such that respective angles between respectively adjacent spines are approximately equal. While the preferred embodiment includes six spines, it is within the scope of the invention to have any number of spines from four to twelve.

Of note is that the cloverleaf structure 300 also defines a central cutout C0 with a negative or empty area A0 disposed about the longitudinal axis 86. In particular, the cloverleaf structure 300 can be delineated by the following structures: a sinusoidal-like cloverleaf member 300 extending from one spine 214 to an adjacent spine 214 in a direction e.g., counterclockwise, or clockwise around the longitudinal axis 86. This characteristic of the sinusoidal structure 300 can be seen in FIG. 4B with for example, spine 214 located on radial axis A. Starting from this spine 214 on axis A, a sinusoidal-like cloverleaf member 300 is configured so that it meanders as indicated by dashed line 302 around a portion of the cutout 212 having a negative or open first area A1 which can be approximated by circle R1. As used herein, the term “open area” means the absence of any solid structure to define an empty space. This first open area A1 is approximately 20% that of the central area A0. For convenience, the first open area A1 can be approximated by the first virtual circle R1 that has its center located at a first distance L1 to the longitudinal axis 86. Continuing in FIG. 4B, the sinusoidal cloverleaf member 300 meanders in a counter-clockwise direction from axis A to axis F around a second open area A2 towards an adjacent spine 214 located on axis F. For convenience, the second open area A2 can also be approximated to a second virtual circle R2 having a second open area A2 of approximately 90% of the first open area A1. It is noted that the second virtual circle may have its center of radius R2 located at a second distance L2 smaller than the first distance L1 to the longitudinal axis 86. Continuing towards axis F in FIG. 4B, the sinusoidal cloverleaf member 300 meanders dashed line 302 around a third open area A3 which for convenience is approximated by third virtual circle with radius R3. The third virtual circle has its center for radius R3 located at a third distance L3 to the central axis 86 that is greater than L2 and approximately equal to the first distance L1. Once the sinusoidal cloverleaf member 300 crosses axis F, the structural nomenclatures repeat again with another first open area A1 on the other side of axis F closer to axis E on which sinusoidal cloverleaf member 300 meanders as referenced by dashed line 302 towards next spine 214 located on axis E. Sinusoidal cloverleaf member 300 may include a plurality of distal facing portions 307 and a plurality of proximal facing portions 309. Additionally, as shown in FIGS. 2A, 3A, 3B, and 4A, 4B, the sinusoidal cloverleaf member 300 may include at least one side connector 305 connecting two adjacent distal facing portions 307 to one another. Each of the side connectors 305 may have a width W1 ranging from approximately 0.1 mm to approximately 0.4 mm and a length L4 ranging from approximately 0.1 mm to approximately 0.4 mm. The one or more connectors 305 may separate the first open area A1 and third open area A3 from the central area A0.

In FIG. 4B, a width T0 of the spine 214 can be from 0.25 to 1 mm while the sinusoidal member 302 has a maximum width T1 of about ½ of the width of T0 with a minimum width T2 of about ⅓ of spine width T0. A width T3 proximate the spine axis (A, B, C, D, E or F) is about the same as the maximum with T1. The central area A0, approximated by radius R0, is approximately 0.8 mm-squared, the fourth virtual circle C4 may have an area approximately 14 times greater than the central area A0. Each of the first and third virtual circle R1 and R3 is located at a first distance L1 of approximately 1.5 mm from the central axis 86 while the second virtual circle R2 is located at a distance L2 of approximately ½ that of the first distance L1.

Preferably, the plurality of spines 214 can be made from a material including nitinol, cobalt chromium, stainless steel, titanium, and combinations or alloys hereof. Each electrode 40 can be made of a material selected from stainless steel, cobalt chromium, gold, platinum, palladium, and alloys hereof.

The inventors have devised the cloverleaf structure 300 in order to allow the basket assembly 38 to be compressed from a maximum diameter of the basket of approximately 32 mm to fit within an 8-12 French sheath without buckling or causing permanent plastic deformation to the spines 214 at any part of the basket assembly 38. In an alternative embodiment, if the number of spines is increased the size of the sheath may be increased to up to 14.5 French to accommodate the additional spines. By virtue of this design, the inventors have been able to compress the basket into a sheath and deploy for full expansion for at least 40 times without any physical sign of buckling.

Referring back to FIG. 4A, it is noted that the sinusoidal-like cloverleaf member 300 is configured so that a portion of cloverleaf member 300 is tangential to the central circle C0 proximate a location between any two radial axes on which two neighboring spines 214 are located. For example, with spine 214 on radii axis A neighboring spine 214 on axis B, the sinusoidal cloverleaf member 300 is tangential to the open circle C0 at a location bisecting the two radial axis A and B by a line Q1 connected to the central axis 86. This tangential characteristic of the sinusoidal cloverleaf member 300 around the open area A0 is repeated for any two adjacent spines 214 as spine 214 on axis B and spine 214 on axis C and so on for all of the bisecting axes Q1, Q2, Q3, Q4, Q5, Q6. The bisecting axes Q1, Q2, Q3, Q4 correspond to peaks of the sinusoidal cloverleaf member 300 and the radial axes A, B, C, D, E, F correspond to troughs of the sinusoidal cloverleaf, wherein peaks of the sinusoidal member are closer to the central axis 86 and troughs are further from the central axis 86.

Another notable feature of the basket structure 38 is a concavity 305 of the distal central portion 211 (FIG. 3A) that can be seen with reference to FIGS. 5A and 5B. In FIG. 5A, it can be seen that the cloverleaf structure 300 is bent so that its open center 211 is contiguous to a plane defined by central circle C0 and spaced apart by a gap G with respect to a plane defined by the fourth virtual circle C4 encircling the cloverleaf structure 300. The concavity is indicated by a virtual circle 88 and a dashed line 305 representing the compound curvature generated by the cloverleaf structure 300 about the central axis 86.

FIG. 6A illustrates the electrode 40 an end front view and FIG. 6B illustrates the same electrode from a top-down perspective view of electrode 40, in accordance with an embodiment of the present invention. Each electrode 40 is fabricated from a biocompatible electrically conductive material, such as platinum, palladium, iridium or gold and alloys of such metals. Each end (one shown in FIG. 6A) of electrode 40 is provided with generally flat lands 82 surrounding a lumen 70 with curved outer surfaces 80 surrounding the lands 82. Electrode 40 has a tissue facing surface with a generally flat top surface 78 with curved outer perimeter 80 surrounding the generally flat top surface 78. The lumen 70 (i.e., a hollow through opening) extends along longitudinal axis 86 therethrough. In addition to the tissue contacting outer surface, each given electrode 40 has an inner surface 76 defined by its lumen 70 on which spine 214 can be inserted through the lumen 70. Electrical wire or electrical trace 41 (FIG. 2C, sufficiently sized to deliver current pulses of at least 10 amps) can be connected to a connection point on the electrode (outside or inside surface). Preferably, wire 41 is electrically connected to a connection point 43 on the inside surface 76 of lumen 70. The cross-section of the electrode can be ovoid, trapezoidal, or substantially ovoid or trapezoidal shape as shown in FIGS. 6A and 6B.

FIG. 7A is a perspective view of another example basket assembly 38 b of a medical probe in an expanded form and including a coated distal end 39. The distal end 39 includes an atraumatic coating 45 configured to reduce likelihood of tissue damage due to pressure of the distal end 39 of the basket assembly 38 b against tissue. The coating 45 covers the sinusoidal-like member 300 and covers the central cutout A0 circumscribed by the sinusoidal-like member 300. The coating 45 can be applied to alternative configurations of basket assembly 38 b as understood by one skilled in the art to reduce likelihood of tissue damage due to pressure of the distal end 39 of the basket assembly 38 b against tissue. The coating 45 may be particularly suited for basket assembly structures having an open distal end. The coating 45 may also be particularly suited for basket assembly structures having struts or structures with edges positioned at the distal end of the basket assembly.

FIG. 7B illustrates the spine structure as formed from a tube stock and including the coating 45 at the distal end. The coating 45 preferably includes a polymeric material. The coating 45 can be applied to the basket assembly 38 b by dipping the distal end 39 in a liquid polymer and curing the polymer to form a flexible membrane. The distal end 39 can be dipped when the basket assembly is in an expanded form as illustrated in FIG. 7A, when the basket assembly is collapsed to a tubular shape similar to as illustrated in FIG. 7B, or at a partially expanded state between the states illustrated in FIGS. 7A and 7B. The distal end 39 can be expanded to the expanded form as illustrated in FIG. 7A as the coating 45 is cured to take its final shape.

FIG. 7C illustrates a perspective view of a distal end 39 of another example basket assembly 38 c of the medical probe in an expanded form and including a coating 45 a with a central opening 47. The central opening 47 may allow for the basket assembly 38 c to be easier to collapse compared to the coating 45 illustrated in FIGS. 7A and 7B.

The embodiments described above are cited by way of example, and the present invention is not limited by what has been particularly shown and described hereinabove. Rather, the scope of the invention includes both combinations and sub combinations of the various features described and illustrated hereinabove, as well as variations and modifications thereof which would occur to persons skilled in the art upon reading the foregoing description and which are not disclosed in the prior art. 

What is claimed is:
 1. An expandable basket assembly for a medical probe, comprising: a plurality of spines extending along a longitudinal axis from a proximal central proximal spine portion to a distal spine portion, the distal spine portion defining a cloverleaf structure disposed radially around the longitudinal axis, the cloverleaf structure defining a central cutout with a central area disposed about the longitudinal axis, the cloverleaf structure comprising: a sinusoidal-like member extending from one spine to an adjacent spine in a direction around the longitudinal axis, the sinusoidal-like member comprises a plurality of distal facing portions, a plurality of proximal facing portions, and at least one side connector connecting two adjacent distal facing portions to one another.
 2. The expandable basket assembly of claim 1, wherein the sinusoidal-like member extends around: (a) a first virtual circle having a first open area of approximately 20% that of the central area, the first virtual circle having its center located at a first distance to the longitudinal axis, (b) a second virtual circle having a second open area of approximately 90% of the first open area, the second virtual circle having its center located at a second distance smaller than the first distance to the longitudinal axis, (c) a third virtual circle having a third open area approximately equal to the first open area, the third virtual circle having its center located at a third distance approximately equal to the first distance to the longitudinal axis, and (d) a fourth virtual circle encircling the sinusoidal-like member comprises an area approximately 14 times greater than the central area and each of the first and third virtual circle is located at a first distance from the central axis while the second virtual circle is located at a second distance of approximately half that of the first distance, and the at least one side connector separating the first and third open areas from the central area.
 3. The expandable basket assembly of claim 1, wherein the at least one side connector comprises two or more side connectors.
 4. The expandable basket assembly of claim 2, in which portions of the sinusoidal-like member are tangential to a virtual sphere with its center disposed substantially on the longitudinal axis so that distal edges of the cutout extend a general direction towards the proximal portion.
 5. The expandable basket assembly of claim 1, wherein the expandable basket assembly comprises a coating covering the sinusoidal-like member and a central cutout circumscribed by the sinusoidal-like member.
 6. The expandable basket assembly of claim 1, wherein each of the spines includes at least one retention member extending generally transverse to the spine.
 7. The expandable basket assembly of claim 6, in which the at least one retention member comprises a bow shaped member.
 8. The expandable basket assembly of claim 6, in which the at least one retention member comprises two bow shaped members disposed in opposite direction and transverse to a longer length of each spine.
 9. The expandable basket assembly of claim 6, in which the at least one retention member comprises first and second sets of retention members spaced apart along the spines, the first set includes two bow shaped members disposed in opposite direction and transverse to a longer length of each spine and the second set includes two bow shaped members disposed in opposite direction and transverse to a longer length of each spine so that each electrode is captured between the first and second sets of retention members.
 10. The expandable basket assembly of claim 1, wherein side connectors have a width ranging from approximately 0.1 mm to approximately 0.4 mm and a length ranging from approximately 0.1 mm to approximately 0.4.mm.
 11. The expandable basket assembly of claim 1, wherein the plurality of spines is configured form an approximately oblate-spheroid basket assembly when in the expanded form.
 12. A medical probe, comprising: a tubular shaft including a proximal end and a distal end, the tubular shaft extending along a longitudinal axis of the medical probe; and an expandable basket assembly coupled to the distal end of the tubular shaft, the basket assembly comprising: a plurality of spines extending along a longitudinal axis from a proximal central proximal spine portion to a distal spine portion, the distal spine portion defining a cloverleaf structure disposed radially around the longitudinal axis, the cloverleaf structure defining a central cutout with a central area disposed about the longitudinal axis, the cloverleaf structure comprising: a sinusoidal-like member extending from one spine to an adjacent spine in a direction around the longitudinal axis, the sinusoidal-like member comprises a plurality of distal facing portions, a plurality of proximal facing portions, and at least one side connector connecting two adjacent distal facing portions to one another.
 13. The medical prob of claim 12, wherein the sinusoidal-like member extends around: (a) a first virtual circle having a first open area of approximately 20% that of the central area, the first virtual circle having its center located at a first distance to the longitudinal axis, (b) a second virtual circle having a second open area of approximately 90% of the first open area, the second virtual circle having its center located at a second distance smaller than the first distance to the longitudinal axis, (c) a third virtual circle having a third open area approximately equal to the first open area, the third virtual circle having its center located at a third distance approximately equal to the first distance to the longitudinal axis, and (d) a fourth virtual circle encircling the sinusoidal-like member comprises an area approximately 14 times greater than the central area and each of the first and third virtual circle is located at a first distance from the central axis while the second virtual circle is located at a second distance of approximately half that of the first distance, and the at least one side connector separating the first and third open areas from the central area.
 14. The medical probe of claim 12, further comprising: a plurality of electrodes, each electrode of the plurality of electrodes comprises a body defining a hollow portion extending through the body of the electrode so that a spine can be inserted into the hollow portion and retained by the at least one retention member, and the at least one side connector comprises two or more side connectors.
 15. The medical probe of claim 12, further comprising a plurality of electrically insulative jackets each disposed between a respective spine of the plurality of spines and a respective electrode, thereby electrically isolating the respective electrode from the respective spine.
 16. The medical probe of claim 12, wherein side connectors have a width ranging from approximately 0.1 mm to approximately 0.4 mm and a length ranging from approximately 0.1 mm to approximately 0.4 mm.
 17. The medical probe of claim 12, further comprising: a wire disposed inside a respective jacket the plurality of electrically insulative jackets, the wire is electrically connected to the respective electrode.
 18. The medical probe of claim 12, wherein the plurality of spines is configured to form an approximately spherically-shaped basket assembly when in the expanded form.
 19. The medical probe of claim 12, in which the central cutout approximates a central circle with the central area, the cloverleaf structure is disposed within a fourth circle with its center on the longitudinal axis so that portions of the cloverleaf close to the center circle is spaced apart along the longitudinal axis with respect to portions of the cloverleaf close to the fourth circle thereby defining a concave cloverleaf structure.
 20. The medical probe of claim 12, in which the cloverleaf structure is concave with its center extending towards the proximal central spine portion of the basket to approximate a concave surface disposed about the longitudinal axis. 